UPSC Prelims 2003 · General Studies

Question 45: Science and Technology

Consider the following statements The purpose of adding sodium sulphate and sodium silicate to the detergent in a washing powder is

1.To keep the washing powder dry
2.To maintain the alkalinity of the powder

Which of these statements is/are correct?

aOnly 1

bOnly 2

cBoth 1 and 2

dNeither 1 nor 2

AnswerThe answer is (c).

Sodium sulphate acts as a filler that keeps the washing powder dry and free-flowing, so it does not cake. Sodium silicate gives the powder its mild alkalinity, which helps the cleaning, and also protects washing machine parts from corrosion. Both statements are therefore accepted as correct. Remember that the builders and fillers in a detergent each do a separate job.

1. Sodium sulphate keeps the powder dry and free-flowing.
2. Sodium silicate keeps the powder mildly alkaline, which helps remove dirt and grease.

Why each option is right or wrong

(a) Statement 2 is also correct, so 'only 1' is incomplete.
(b) Statement 1 is also correct, so 'only 2' is incomplete.
(c) Correct: both statements hold.
(d) Both statements hold, so 'neither' is wrong.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.